The light on my landing flashes on and off when the switch is in the off position, I think if I change the positions of the light switch downstairs it stops but as it is totally random I have not been able to actualy confirm this, the switch downstairs controls both the lounge light and landing which are on seperate rings. In addition to this the smoke alarm started randomly going off in short bursts last night, this takes it 's power from the landing light so i am thinking it is connected to the flashing bulb.

My take is that the switch downstairs is faulty, letting current pass through from the downstairs to the upstairs ring giving the bulb (compact flourescent) a short 'pulse' of power. As it is a 15 quid switch I don't really want to replace unless I am sure it is at fault

Thanks for the replies. It's not a dimmer, just a 2g toggle type switch.

If it's not dangerous thats great but my main concern now is the smoke alarm going off randomly. It has happened a few times now, including at 3am last night which scared the **** out of me and the wife, my daughter slept through it somehow even though it's outside her room